Methane Emission from Paddy Soils as Influenced by Application of Organic Manure,Soil Available Copper and Nitrogen

Based on an outdoor pot experiment w ith 18paddy soils conducted in 2000d uring rice growing season 8 ,ten out of the 18soils were selected to further perfo rman outdoor pot experiment in 2001r ice growing season.Two treatments w ere designed as mineral fertilization(MF )and mineral fertilizer +wheat straw incorporation(MF +WS ).Seasonal average rate of CH 4 emission fromthe MF treatment ranged from0.89to 5.92mg ·m -2 ·h -1 .Incorporation of wheat straw enhan ced considerably CH 4 emission,some 2.0～8.3times higher than that from the MF treatment.Seasonal average of CH 4 emission was found to negatively correlateNH 4+ -N concentration in the floodwater,yielding the correlation coefficient s of -0.6953  and -0.5605for the treatments of MF a nd MF +WS,respectively.Negative correlation of the seasonal average emis sion against available copper concentration in the soils was also observed.The correlation coefficient was,respectively,-0.8654  and -0.7966  for the treatments of MF and MF +WS.A further investigation indicated that wheat straw incorporation di d not enhance the concentration of di ssolved organic carbon(DOC)in the soils.Methane emission fromt he MF treatment was positively assoc iated with the DOCconcentration(r=0.9030  ).Moreover,the DOC concentration correlated negatively to the available copper concentration,suggesting t hat a higher concentration of available copper chelate more roo t exudation and yield carbon -copper compound,facilitating reduction o f the availability of methanogenic substrates in the soil.